The present invention relates to a thermal swing carbon dioxide recovery concentration apparatus which can recover by a high recovery rate, can condense to high concentration, and can miniaturize, has high endurance, can utilize waste heat 100° C. or less, and consumes less energy.
The effort to reduce carbon dioxide emitted from industry, cars, and homes as much as possible as a measure against global warming is being made on the world level. Specifically, it is such effort that old devices that consume energy are improved and replaced to produce energy saving effects. Also, to generate energy such as power generation, devices that utilize renewable energy such as sunlight and wind power are used. In addition, improvements are made to increase the power generation efficiency of the thermal power plants. Furthermore, the technologies for recovering and concentrating carbon dioxide discharged from thermal power plants and for storing it underground and in the deep sea have been also researched and developed for the future.
The technology for recovering and condensing carbon dioxide from the gas discharged from a thermal power plant, a combustion furnace, etc. is one focus of the present inventor.
The most popular thermal power plants use oil, natural gas and coal for fuel. In addition, there are some other thermal power plants which incinerate the garbage discharged from cities. In such thermal power plants, some which use coal as fuel have the following features. That is, coal is inexpensive as fuel, coal world reserves are much larger than oil and the reserves are located all over the world, therefore, it is easy to obtain and can supply electricity steadily.
However, coal has a problem that coal emits more carbon dioxide at the time of combustion as compared with oil or natural gas. Similarly, coal also emits much sulfide. Not only coal but heavy oil also has the same problem as coal. For this reason, in the plants which use coal or heavy crude oil as fuel, devices to remove SOx and nitrogen oxide have been provided, and environmental pollution is prevented.
However, even if SOx and nitrogen oxide are removed to prevent environmental pollution, carbon dioxide is still emitted so much that there is a problem of promoting global warming.
As a measure for improvement, research and development are being made on a technique of separating, recovering and concentrating carbon dioxide from exhaust gas, and storing the recovered carbon dioxide in the soil or the deep ocean. Various proposals such as a deep freeze method, an absorption method, an adsorption method, a membrane separation method, etc. have been proposed as means for separating, recovering and concentrating this carbon dioxide.
A deep freeze method is the method of pressurizing material gas to carry out liquefaction separation of the carbon dioxide under pressure by using the difference in the liquefaction temperatures of each gas. This method requires electric power for the compressor which compresses the gas and electric power for the freezer which carries out the deep freeze. For example, in a case where dioxide levels are just over or below 10%, the remaining 90% gases which do not need to be recovered, gases other than carbon dioxide, are necessarily also subjected to compression and deep freeze. Therefore, this method has such fault that energy expenditure becomes excessive.
The absorbing method is a method of desorbing carbon dioxide and condensing it by making an alkaline fluid of amine systems such as monoethanolamine absorb carbon dioxide, recovering and heating it. Although this method is already put in practical use, due to dealing with the alkaline fluid, an expensive corrosion-resistant material is needed. Therefore, the method is expensive. In addition, since the concentration of the amine aqueous solution is around 30% and water is around 70%, the heat capacity of the liquid to be handled becomes enormous. Even if a heat exchanger is placed in the necessary place and heat is recovered, the energy saving is approaching to its limit. (non-Patent document 2) Further, since monoethanolamine and the like are chemicals to be vaporized, there is a problem that secondary contamination is a concern if the gases are exhausted into the atmosphere.
The adsorption method uses a gas adsorption material such as zeolite or activated carbon, and the method can be a pressure swing method or a thermal swing method. The pressure swing method (hereinafter referred to as “PSA”) adsorbs and desorbs using a pressure difference, and the thermal swing method adsorbs and desorbs using a temperature difference (hereinafter referred to as “TSA”). The PSA method uses the principle in which the amount of adsorption of carbon dioxide changes with pressure. Since, in the PSA method, carbon dioxide is separated and adsorbed by pressuring and carbon dioxide is desorbed and recovered by decompressing, a capacity-to-resist-pressure container is required as are precision instruments such as an electromagnetic valve, a compressor, and a vacuum pump, and there is such a problem that enlargement is difficult.
The TSA method absorbs carbon dioxide at a temperature below Centigrade 50° C. (let all temperature be “Centigrade” henceforth). At a temperature of around 100-200° C., carbon dioxide is desorbed to recover it. In a multi-tower system in which a plurality of adsorption towers packed with a carbon dioxide adsorbent are alternately switched between adsorption and regeneration, the pressure loss of gas is high, and fluctuations in concentration and pressure due to switching of the above-stated towers are inevitable. In addition, there are drawbacks such as difficulty in upsizing.
Also, in the TSA method, low-pressure power loss and/or enlargement of the device are addressed by using a rotating adsorption type honeycomb rotor as described in the Patent Documents 3 through 5. However, this method is insufficient with respect to the recovery rate of carbon dioxide, the concentration of carbon dioxide when concentrated, and the energy-saving nature of recovery energy.